Pick with Threaded Shank

ABSTRACT

A degradation assembly may comprise a block secured to a surface. The degradation assembly may also comprise a pick comprising a working end and a shank. The shank may comprise a continuous external circumference and a shank thread form configured to secure the shank within the block, or within a holder secured within the block.

BACKGROUND OF THE INVENTION

The present invention relates to picks or bits used to degrade surfaces, specifically to picks or bits used in mining, trenching and road milling operations. It was formerly believed that allowing a pick to rotate within a block may be beneficial in that it may result in a more even wear on the pick rather than having the wear concentrated on one side. To protect the block from wear due to the rotating pick, a bit holder or sleeve was sometimes disposed between the pick and the block. For example, U.S. Pat. No. 5,098,167 to Latham, which is herein incorporated by reference for all that it contains, discloses a sleeve containing a bit for use on a roadway surface reclaiming machine in a removable manner which aids in protecting the block from abrasion. To decrease abrasion between the confronting surfaces of the block and the sleeve, and to increase the useful life of the pick, the sleeve may be threaded into the block in such a manner that contact by abrasive material with the sleeve tightens the connection between the block and the sleeve.

It has since been discovered that diamond enhanced picks may last longer despite uneven wear when non-rotatable. U.S. Pat. Pub. No. 2009/0273225 to Hall et al., which is herein incorporated by reference for all that it contains, discloses a pick shank press fit within a bore of a pick holder. The pick may comprise a diamond enhanced tip and may be rotationally fixed within a bore of the holder. The shank may comprise at least one longitudinal slot extending along the shank from a distal end of the shank. The slot allows the shank to resiliently collapse upon insertion into the bore while still allowing the shank to maintain a press fit while within the bore.

Despite the advancements as shown in the prior art, it is believed that there is still a need to develop better means to rotationally secure picks or bits.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a degradation assembly may comprise a block secured to a surface. The degradation assembly may also comprise a pick comprising a working end and a shank. The shank may comprise a continuous external circumference and a shank thread form configured to secure the shank within the block. The shank thread form may be disposed on an outer surface of the shank.

The block may comprise a bore there through. A block thread form may be disposed within the bore and may be configured to mate with the shank thread form. The shank thread form may also comprise a buffer pad configured to clean the block thread form as the shank thread form is mated with the block thread form. The shank thread form and the block thread form may be collectively configured to prevent the pick from rotating within the block while in operation or to tighten due to impacts on the working end while in operation.

The shank may comprise a solid cross-section or the shank may be hollow. When hollow, the shank thread form may be disposed on an internal surface of the shank. In this embodiment, the shank thread form may taper inwardly towards the working end.

The shank may comprise a tapered section. The tapered section may be formed between the shank thread form and the working end and the tapered section may be configured to provide an interference fit between the shank and the block. The shank thread form may be disposed on the tapered section. The tapered section may be configured to resist a majority of the working torque between the pick and the block while in operation. The working end may comprise a tip comprising a superhard material.

The pick may comprise a reduced cross-section between the shank and the working end to provide a predetermined area of failure.

In another aspect of the present invention, a degradation assembly may comprise a block secured to a surface, a holder secured within the block, and a pick comprising a working end and a shank. The shank may comprise a continuous external circumference and the shank thread form may be configured to secure the shank within the holder. In this embodiment, the holder may comprise a bore there through. The holder may be secured within the block by an interference fit or spring clamp.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures further describe the invention.

FIG. 1 is a partially cut-away view of an embodiment of a degradation drum on a road milling machine.

FIG. 2 a is a perspective view of an embodiment of a pick.

FIG. 2 b is a cross-sectional view of an embodiment of a pick secured in a block.

FIG. 3 a is a perspective view of an embodiment of a pick with a tapered shank.

FIG. 3 b is a cross-sectional view of an embodiment of a pick with a tapered shank secured in a block.

FIG. 4 a is a perspective view of another embodiment of a pick with a tapered shank.

FIG. 4 b is a cross-sectional view of another embodiment of a pick with a tapered shank secured in a block.

FIG. 5 a is a cross-sectional view of an embodiment of a pick with a hollow shank.

FIG. 5 b is a cross-sectional view of an embodiment of a pick with a hollow shank secured in a block.

FIG. 6 is a cross-sectional view of an embodiment of a pick with a hollow shank and tapered shank thread form.

FIG. 7 is a perspective view of an embodiment of a pick and a holder.

FIG. 8 is a perspective view of an embodiment of a pick with a tapered shank and holder.

FIG. 9 a is a perspective view of another embodiment of a pick and holder.

FIG. 9 b is a cross-sectional view of an embodiment of a pick and a holder secured in a block.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

Referring now to the figures, FIG. 1 discloses an embodiment of a road milling machine 101. The road milling machine 101 also known as a cold planer, may be used to degrade natural formations 102 such as pavement, concrete or asphalt prior to placement of a new layer. The arrow 103 shows the machine's direction of travel.

The road milling machine 101 may comprise a degradation drum 104. The degradation drum 104 may comprise a plurality of blocks 105 secured to its outer surface. A pick 106 may be secured within each block 105. During normal operation, the degradation drum 104 may rotate causing the picks 106 to engage and degrade the formation 102. In other embodiments of the present invention, blocks may be secured to surfaces of drums, chains, or other moving parts of mining, trenching or road milling machines to cause picks to engage and degrade formations of all types. In some embodiments, each pick may be disposed within a holder, and a holder may be secured within each block.

FIG. 2 a discloses an embodiment of a pick 201. The pick 201 may comprise a pick body 204 in between a working end 206 and a shank 202. The working end 206 may directly engage a formation. The working end 206 may comprise a substantially conical shape and a tip 211. The tip 211 may comprise a superhard material selected to reduce wear and extend service life. The superhard material may comprise natural diamond, synthetic diamond, polycrystalline diamond, vapor deposited diamond, cubic boron nitride, diamond impregnated matrix, diamond impregnated carbide, silicon carbide, other superhard material known in the art, or combinations thereof.

The shank 202 may comprise a bottom portion 210. The bottom portion 210 may comprise a continuous external circumference. The shank 202 may comprise a solid cross-section (as shown in this embodiment) or the shank 202 may be hollow. It is believed that a shank 202 comprising a continuous external circumference and solid cross-section may be able to withstand a large amount of load and/or torque without substantially deforming. A shank thread form 205 may be disposed on an outer surface of the shank 202.

FIG. 2 b discloses a cross-sectional view of the pick 201 (as shown in FIG. 2 a) disposed in a block 207. The block 207 may comprise a bore 208 there through. The pick 201 may be disposed within the bore 208 and the shank thread form 205 may be configured to mate with an opposing block thread form 209 disposed within the bore 208 to form a rigid connection. The shank thread form 205 may be disposed on an outer surface and may be square, triangular, trapezoidal, or combinations thereof.

In some embodiments, the shank thread form 205 and the block thread form 209 may be collectively configured to prevent the pick 201 from rotating within the block 207 while in operation. Because the pick 201 may be configured to not rotate within the block 207, due to the nature of thread forms the pick 201 may be also axially fixed within the block 207. In other embodiments, the shank thread form 205 and the block thread form 209 may be collectively configured to tighten due to impacts on the working end 206 while in operation. This may be accomplished by offsetting the position of the working end 206 from a direction of impact such that each impact applies torque to the pick 201 and manufacturing the shank thread form 205 either right-handed or left-handed based on which direction it is offset.

This embodiment further comprises a buffer pad 212 disposed on the shank thread form 205. The buffer pad 212 may clean the mating block thread form 209 as the thread forms rotate with respect to each other. By keeping the thread forms clean, a more secure fit may be possible.

FIG. 3 a discloses an embodiment of a pick 301 with a shank 302 comprising a tapered section 303. A pick body 304 may be disposed between a working end 311 and the shank 302. The tapered section 303 may be configured to taper towards a bottom portion 310 opposite of the working end 311. A shank thread form 305 may be disposed on at least a portion of the tapered section 303.

FIG. 3 b discloses a cross-sectional view of the pick 301 (as shown in FIG. 3 a) disposed in a block 307. It is believed that disposing the shank thread form 305 on the shank's tapered section 303 may require fewer rotations to secure the pick 301 within the block 307.

FIG. 4 a discloses another embodiment of a pick 401 comprising a shank 402 and a tapered section 403. A pick body 404 may comprise a substantially larger cross-section than a working end 406 and the shank 402. The tapered section 403 may be configured to taper towards a bottom portion 410 and begin tapering from the largest cross-section of the pick body 404.

FIG. 4 b discloses a cross-sectional view of the pick 401 (as shown in FIG. 4 a) disposed in a block 407. A shank thread form 405 may be disposed on the tapered section 403. The tapered section 403 may provide an interference fit between the shank 402 and the block 407. The interference fit may prevent excess pressure from being loaded onto the shank thread from 405. The tapered section 403 may thus resist a majority of the working torque between the pick 401 and the block 407 while in operation. The majority of the working torque may be defined as greater than 50% of the torque applied to the pick 401 from the formation during normal working conditions. In some embodiments, the tapered section 403 may be configured to resist over 70% of the working torque.

In some embodiments, the pick 401 may comprise a reduced cross-section 413 disposed between the shank 402 and the working end 406. The reduced cross-section 413 may be configured to provide a predetermined area of failure. During working operations that may cause damage to the shank thread form 405, the working end 406 may break-off at the reduced cross-section 413. As the working end 406 breaks off, the pick 401 may no longer engage the formation and the stress on the shank thread form 405 may be relieved.

FIG. 4 b also comprises an inset disclosing an embodiment of the shank thread form 405. In the embodiment shown, the shank thread form 405 is a trapezoidal thread form and may comprise a plurality of crests 414, roots 415, flanks 416 and pitches 417. The shank thread form 405 may comprise an angle 418 intermediate adjacent flanks 416. It is desirable that the angle 418 be sufficiently large that substantially all aggregate fall out and not get stuck within the shank thread form 405.

FIG. 5 a discloses an embodiment of a pick 501 comprising a working end 506 and a shank 502 wherein the shank 502 is hollow. The shank 502 may comprise an internal surface 519 and a shank thread form 505 may be disposed on the internal surface 519.

FIG. 5 b discloses a cross-sectional view of the pick 501 (as shown in FIG. 5 a) disposed in a block 507. The pick 501 may be disposed within a bore 508 of the block 507 and the bore 508 may be configured to surround the shank 502. A block thread form 509 may be disposed within the bore 508 and may be configured to protrude from a bottom surface of the bore 508 towards the working end 506. The shank thread form 505 may be configured to mate with the block thread form 509. It is believed that the pick 501 may be supported by both the bore 508 and the block thread form 509 during normal working operation.

FIG. 6 discloses an embodiment of a pick 601 comprising the hollow shank 602. A shank thread form 605 may be disposed on an internal surface 619 of the shank 602. The shank thread form 605 may taper inwardly towards a working end 606 of the pick 601.

FIG. 7 discloses an alternative embodiment of a pick 701 and a pick holder 720. The pick 701 may comprise a shank 702 with a shank thread form 705. The shank thread form 705 may mate with a pick holder thread form (not shown) disposed within a bore of the pick holder 720. The pick holder 720 may be configured to fit within a block disposed on a degradation drum. A slot 722 in the pick holder 720 may aid in securing the pick holder 720 within a block.

FIG. 8 discloses an alternative embodiment of a pick 801 comprising a shank 802 with a shank thread form 805 that tapers towards a bottom portion 810 of the shank. The pick 801 may be secured into a pick holder 820 by the shank thread form 805 mating with a pick holder thread form (not shown) disposed within a bore of the pick holder 820.

FIG. 9 a discloses an alternative embodiment of a pick 901 comprising a shank 902 with a shank thread form 905. The pick 901 may be secured into a pick holder 920.

FIG. 9 b discloses a cross-sectional view of the pick 901 (as shown in FIG. 9 a) secured within the pick holder 920 by the shank thread form 905 mating with a pick holder thread form 921 disposed within a bore of the pick holder 920. The pick holder 920 may be disposed within a bore 908 of the block 907 secured by a spring clamp 923 which compresses both the bore 908 of the block 907 and a recessed portion of the shank 924 of the pick holder 920.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention. 

What is claimed is:
 1. A degradation assembly, comprising: a block secured to a surface; and a pick comprising a working end and a shank, wherein the shank comprises a continuous external circumference and a shank thread form configured to secure the shank within the block.
 2. The assembly of claim 1, wherein the shank comprises an outer surface and the shank thread form is disposed on the outer surface.
 3. The assembly of claim 1, wherein the block comprises a bore there through.
 4. The assembly of claim 3, wherein the block comprises a block thread form disposed within the bore and the shank thread form is configured to mate with the block thread form.
 5. The assembly of claim 4, wherein the shank thread form comprises a buffer pad configured to clean the block thread form as the shank thread form is mated with the block thread form.
 6. The assembly of claim 4, wherein the shank thread form and the block thread form are collectively configured to prevent the pick from rotating within the block while in operation.
 7. The assembly of claim 4, wherein the shank thread form and the block thread form are collectively configured to tighten due to impacts on the working end while in operation.
 8. The assembly of claim 1, wherein the shank comprises a solid cross-section.
 9. The assembly of claim 1, wherein the working end comprises a tip comprising a superhard material.
 10. The assembly of claim 1, wherein the shank comprises a tapered section configured to taper toward a bottom portion opposite of the working end.
 11. The assembly of claim 10, wherein the tapered section is formed between the shank thread form and the working end, and the tapered section is configured to provide an interference fit between the shank and the block.
 12. The assembly of claim 10, wherein the shank thread form is disposed on the tapered section.
 13. The assembly of claim 10, wherein the tapered section is configured to resist a majority of the working torque between the pick and the block while in operation.
 14. The assembly of claim 1, wherein the pick comprises a reduced cross-section between the shank and the working end providing a predetermined area of failure.
 15. The assembly of claim 1, wherein the shank is hollow.
 16. The assembly of claim 15, wherein the shank thread form is disposed on an internal surface of the shank.
 17. The assembly of claim 16, wherein the shank thread form tapers inwardly towards the working end.
 18. A degradation assembly, comprising: a block secured to a surface; a holder secured within the block; and a pick comprising a working end and a shank, wherein the shank comprises a continuous external circumference and a shank thread form configured to secure the shank within the holder.
 19. The assembly of claim 18, wherein the holder comprises a bore there through.
 20. The assembly of claim 18, wherein the holder is secured within the block by an interference fit or spring clamp. 